The H.sub.2 -antagonist agents (hereinafter "H.sub.2 -antagonists") are routinely administered orally to patients suffering from gastrointestinal conditions such as ulcers, dyspepsia, various reflux indications and the like. Typically, the H.sub.2 -antagonist is delivered to the patient in tablet or powder-filled capsule form. Other liquid oral compositions such as syrups have also been proposed (see, for example, U.S. Pat. No. 4,128,658 to Price et al.)
The H.sub.2 -antagonists are known to have an unpalatably bitter taste when ingested in any form other than solid capsule or tablet form. However, certain segments of the patient population prefer more easily ingested product forms, including chewable tablets, lozenges or troches. Several attempts, with somewhat limited success, have been made to produce a pharmaceutical composition for oral administration which contains an H.sub.2 -antagonist. For example, U.S. Pat. No. 5,219,563 to Douglas et al. proposes drug adsorbates for masking the bitter taste of ranitidine which include synthetic cation exchange resins. PCT Publication No. WO 94/0856 to Glaxo proposes chewable tablets of ranitidine, which include an intense sweetener such as aspartame. PCT Publication No. WO94/08576 to Glaxo proposes taste-masked compositions of ranitidine comprising a dispersion of lipid coated ranitidine particles in a non-aqueous vehicle. U.S. Pat. No. 5,260,072 to Roche et al. proposes chewable tablets of H.sub.2 -antagonists which contain retrogranules of the drug coated with cellulose acetate, cellulose acetate butyrate or a combination thereof to mask the taste of the H.sub.2 -antagonist. U.S. Pat. No. 5,084,278 to Mehta proposes taste-masked ranitidine chewable tablets containing a medicinal core coated with a polymeric coating. U.S. Pat. No. 5,275,823 to France et al. proposes chewable tablets of cimetidine contaiing hygroscopic water-insoluble substances, such as polysaccharides, as extra-granular excipients.
Attempts at taste-masking other pharmaceutical agents have also been proposed. For example, U.S. Pat. No. 4,711,774 to Denick, Jr. et al. proposes a magnesium aluminum silicate as an adsorbate for analgesics, antiasthmatics, antitussives, antihistamines, and other drugs. U.S. Pat. No. 3,140,978 to Zentner also proposes magnesium aluminum silicate pharmaceutical compositions. Neither of these references discloses or suggests masking the bitter taste of an H.sub.2 -antagonist with aluminum magnesium silicate.
Accordingly, there remains a need in the art for methods of taste-masking H.sub.2 -antagonists for the preparation of oral dosage units containing the same. Moreover, there remains a need in the art for pharmaceutical compositions for the oral administration of H.sub.2 -antagonists.